Regio- and Stereoselective Addition of 1,2,3,6-Tetrahydrophthalimide to Electron-Poor Acetylenic Esters in the Presence of Triphenylphosphine

Abstract

Protonation of the highly reactive 1:1 intermediates, produced in the reaction between triphenylphosphine and dialkyl acetylenedicarboxylates (or alkyl acetylenecarboxylates), by 1,2,3,6-tetrahydrophthalimide leads to vinyltriphenylphosphonium salts, which undergo Michael addition reaction with conjugate base to produce phosphorus ylides. Dipotassium hydrogen phosphate and silica gel were found to catalyze conversion of the phosphorus ylides to electron-poor N-vinyl imides in solvent-free conditions under thermal (80–90°C, 40–50 min) conditions. The structural analysis of the products indicated that the reaction is regio- and stereoselective.

Keywords:

• Acetylenic esters
• dipotassium hydrogen phosphate
• electron-poor N-vinyl imide
• regioselective
• stereoselective
• silica gel
• vinyltriphenylphosphonium salt

Acknowledgments

The authors are thankful to the Research Council of Zanjan Islamic Azad University for support of this work.